This invention relates a process for the manufacture of 1,3,3,3-tetrafluoropropene (HFC-1234ze). More particularly, the invention pertains to a process for the manufacture of HFC-1234ze by a two stage vapor phase process. The process comprises a hydrofluorination of 1-chloro-3,3,3-trifluoropropene (HCFC-1233zd) into 1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa) and 1,1,1,3,3-pentafluoropropane (HFC-245fa), followed by the dehydrochlorination of HCFC-244fa and dehydrofluorination of HFC-245fa.
Traditionally, chlorofluorocarbons (CFCs) like trichlorofluoromethane and dichlorodifluoromethane have been used as refrigerants, blowing agents and diluents for gaseous sterilization. In recent years, there has been widespread concern that certain chlorofluorocarbons might be detrimental to the Earth's ozone layer. As a result, there is a worldwide effort to use halocarbons which contain fewer or no chlorine substituents. Accordingly, the production of hydrofluorocarbons, or compounds containing only carbon, hydrogen and fluorine, has been the subject of increasing interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. In this regard, 1,3,3,3-tetrafluoropropene (HFC-1234ze) is a compound that has the potential to be used as a zero Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP) refrigerant, blowing agent, aerosol propellant, solvent, etc, and also as a fluorinated monomer.
It is known in the art to produce HFC-1234ze. For example, U.S. Pat. No. 5,710,352 teaches the fluorination of 1,1,1,3,3-pentachloropropane (HCC-240fa) to form HCFC-1233zd and a small amount of HFC-1234ze. U.S. Pat. No. 5,895,825 teaches the fluorination of HCFC-1233zd to form HFC-1234ze. U.S. Pat. No. 6,472,573 also teaches the fluorination of HCFC-1233zd to form HFC-1234ze. U.S. Pat. No. 6,124,510 teaches the formation of cis and trans isomers of HFC-1234ze by the dehydrofluorination of HFC-245fa using either a strong base or a chromium-based catalyst. Additionally, European patent EP 0939071 describes the formation of HFC-245fa via the fluorination of HCC-240fa through intermediate reaction product which is an azeotropic mixture of HCFC-1233zd and HFC-1234ze.
It has been determined that these known processes are not economical relative to their product yield. Accordingly, the present invention provides an alternate process for forming HFC-1234ze which is more economical than prior art processes and at a higher yield as compared to known processes. In particular, it has now been found that HFC-1234ze may be formed by a two step reaction involving the hydrofluorination of 1-chloro-3,3,3-trifluoropropene (HCFC-1233zd) into 1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa) and subsequent fluorination of the HCFC244fa to form 1,1,1,3,3-pentafluoropropane (HFC-245fa), followed by the dehydrochlorination of HCFC-244fa and dehydrofluorination of HFC-245fa via reaction with a caustic solution. Alternately, the dehydrochlorination of HCFC-244fa and dehydrofluorination of HFC-245fa may be undertaken by thermal decomposition in the absence of or in the presence of a catalyst.